More specifically, the invention relates to a blow-molding installation for manufacturing thermoplastic hollow bodies by blow-molding or stretch-blow-molding containers in a molding cavity of a mold, this blow-molding installation comprising a nozzle actuator comprising at least one moving nozzle piston, a nozzle able to establish a sealed fluidic connection with the neck of a container placed in the molding cavity, and pneumatic means for operating the actuator between a raised position in which the nozzle is raised above the mold and a blow-molding position in which the nozzle makes a sealed fluidic connection with the neck of a container placed in the molding cavity.
The expression “hollow body” is to be understood as meaning any hollow element which, when heated and blow-molded or stretch-blow-molded, is able to form a container and has a body part and a neck part, the neck having already been produced to the definitive shape and size of the neck of the container. A hollow body is therefore either a preform prior to the first blow-molding or stretch-blow-molding step, or an intermediate container which has already undergone a blow-molding or stretch-blow-molding operation and, having been reheated, needs to be blow-molded or stretch-blow-molded again.
There are two types of blow-molding nozzles commonly used for performing this blow-molding operation once the hollow body has been placed in the mold with the neck projecting from the mold.
A first type of nozzle commonly used is, as illustrated in FIG. 7 of document FR 2 790 704, a nozzle able to create sealed contact with the mouth of the neck of the hollow body, that is to say a nozzle having a blow-molding tube of which the free end, usually termed the “nozzle orifice” is able to collaborate sealingly with the mouth of the neck. In general, the nozzle orifice has a frustoconical external shape and the diameter at the base of the cone frustum is smaller than that of the opening of the neck thus allowing the blow-molding tube of the nozzle to be introduced into the neck. Because of the increase in diameter of the frustoconical section, contact is made between the cone frustum and the interior peripheral edge of the mouth of the neck of the preform, thus establishing sealed contact between the neck and the nozzle during the blowing operation. Alternatively, the end of the nozzle has an external shoulder against which the mouth of the neck of the preform bears, thus making it possible to establish sealed contact between the neck and the shoulder of the blowing tube of the nozzle. In this case, the free end of the blowing tube may be made substantially cylindrical. Nozzles of the type which establish sealed contact with the mouth are, in practice, given preference in the manufacture of heat-resistant containers intended to contain hot-filled liquids.
A second type of nozzle also commonly used is termed the “bell nozzle”, particularly like the one described in document FR 2 764 544 or also illustrated in FIG. 1 of document FR 2 790 704. A bell nozzle comprises a tube with a blowing end surrounded by a skirt. When the nozzle is in the blow-molding position, the bell-shaped end of the nozzle caps the neck of the preform, the skirt then bearing sealingly against the upper surface of the mold. Bell-type nozzles are, in practice, given preference in the manufacture of containers intended to contain carbonated liquids.
To allow the nozzles to be lowered toward the necks of the preforms and to form a sealed fluidic connection between the neck of the preform and the end of the blowing tube, either directly by the end of the blowing tube bearing on and/or being inserted in the neck when using a nozzle of the type which makes sealed contact with the mouth, or indirectly when using a nozzle of the bell type, each type of nozzle is associated with a respective one of two types of actuator, the structures and operating modes of which are determined according to the type of nozzle. It is therefore necessary to modify a large proportion of the blow-molding installation when switching from the manufacture of one type of container to the manufacture of containers of the other type.
To do this, relatively lengthy conversion operations have to be performed on the blow-molding installation. Specifically, the nozzle actuators have then to be disconnected, the actuators have to be exchanged, other actuators need to be connected with the new nozzles and then the new actuator operating mode needs to be initialized for the new container manufacturing run.
In molding installations of the rotary carousel type equipped with a great many molds (several tens of molds, typically of the order of twenty to forty molds), these connecting/disconnecting/initializing operations prove to be particularly lengthy, and therefore expensive, while at the same time requiring the participation of qualified staff.
It would therefore be particularly advantageous to use means that allow the blow-molding installation to be adapted in the swiftest possible length of time, easily, using simple mechanical means and without involving reinitializing the actuator operating mode.
The present invention proposes to solve these problems associated with the prior art.